Marble Tower – riding the rails

The joy and fascination of getting the marble dispensing mechanism working was kept in check by the finicky nature of the mechanism. Once attached to the tower I found that the tolerance for being off level was less than my tolerance for marbles cascading over the edges and scattering around the workshop. This was the second stage of procrastination.

Once I got over the fact that I would be revisiting the dispensing mechanism, I pushed forth to work on the guts of the tower. The next step was to attach rails around the inside edge of the tower on a slight decline, taking the marbles 360 degrees around the tower and dropping them into the next stage.

We’re back to compound miters again, but compound compound miters. In this stage, the Lee Valley errata suggests an easy out, instead of nestling the miters up against the joint to the rails, put a butt joint to the rails and have the miter joint out in the space between the rails. I did not heed this advice, thinking it sounded too wimpy. Next time, I’ll think about it more and maybe try out a couple before committing to doing it the hard way.

I fought with these miters for multiple sessions and finally found a system of making the initial cuts on a chop saw and fine tuning them on the stationary disk sander. Not terribly satisfying work, but once it was up and working, I was pretty happy with it.

At this point I learned that I had made a couple of mistakes.

1 – the coves for the rails should have been a bit deeper. I did follow the plans for this, but I believe there is plenty of material to have deeper coves which would result in the marbles staying on the rails more readily. When the marbles get up some speed on the rails there is a chance they will bounce off a corner and actually jump off the rails.
I took out some carving gouges and deepened the coves slightly at the corners and that has mostly solved the problem. If the final setup still has the problem I may take the advice laid out in the plans and put in some raised strips to deflect the marbles back onto the rails.

2 – I was a bit too generous with the downward angle of this section. This essentially had two negative effects. The first was the increased speed and potential to jump the rails, the second was that I had not eaten into the space for the sections below it. This comes back to bite me later as I compound the problem in a later stage as well. Duh!